WO2019017858A2 - Twin roll casting method with magnetic stirrer - Google Patents

Twin roll casting method with magnetic stirrer Download PDF

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Publication number
WO2019017858A2
WO2019017858A2 PCT/TR2017/050566 TR2017050566W WO2019017858A2 WO 2019017858 A2 WO2019017858 A2 WO 2019017858A2 TR 2017050566 W TR2017050566 W TR 2017050566W WO 2019017858 A2 WO2019017858 A2 WO 2019017858A2
Authority
WO
WIPO (PCT)
Prior art keywords
magnetic stirrer
twin roll
launder
roll casting
particles
Prior art date
Application number
PCT/TR2017/050566
Other languages
French (fr)
Other versions
WO2019017858A3 (en
Inventor
Mustafa Murat DUNDAR
Aziz DURSUN
Onur BIRBASAR
Vedat TOPALOGLU
Baris YAZAR
Original Assignee
Assan Aluminyum San. Ve Tic. A. S.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to TR2017/00428 priority Critical
Priority to TR201700428 priority
Application filed by Assan Aluminyum San. Ve Tic. A. S. filed Critical Assan Aluminyum San. Ve Tic. A. S.
Publication of WO2019017858A2 publication Critical patent/WO2019017858A2/en
Publication of WO2019017858A3 publication Critical patent/WO2019017858A3/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0622Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10Supplying or treating molten metal
    • B22D11/11Treating the molten metal
    • B22D11/114Treating the molten metal by using agitating or vibrating means
    • B22D11/115Treating the molten metal by using agitating or vibrating means by using magnetic fields

Abstract

The invention relates to a configuration comprising a magnetic stirrer in the launder region, which improves the efficiency of the twin roll casting process used during the production of strip and foil with aluminum alloy, improves product quality and provides a homogeneous mixture during casting.

Description

TWIN ROLL CASTING METHOD WITH MAGNETIC STIRRER FIELD OF THE ART
The invention relates to a kind of magnetic stirrer application which, in the twin roll casting process, prevents agglomeration and settling down of grain refining particles in the liquid metal, ensures a homogeneous distribution and enhances the quality of the aluminum strip.
PRIOR ART
The changing human needs in the modern world have increased the use of all forms of aluminum in daily life due to many different reasons. In parallel with the developing technology, production quantities have increased, production costs have decreased and as a result the amount of aluminum usage per person has increased rapidly.
Twin Roll Casting (TRC) technique is one of the aluminum strip and foil production method. Starting from the 1950's, the amount of aluminum foil and strip produced by using this method have increased day by day. The lower initial investment cost and lower operational costs compared to the cost structure of aluminum strip and foil production with conventional methods have made the Twin Roller Casting technique attractive to manufacturers.
In the casting phase of the foil and strip production, agents in the form of aluminum rods comprising particles with the stochiometry of T1B2 and additional Ti element present in the form of AI3T1 is added into the liquid metal in order to initiate nucleation during solidification of the liquid metal and to refine grain structure. In this way, an effective grain refinement mechanism is provided for solidification of the mentioned aluminum alloy. Aluminum alloy with fine grain structure has tendency of forming less segregation in the microstructure and high mechanical properties. The addition rate of grain refiner rod is determined by the amount of Ti measured in the liquid metal composition.
In the twin-roll casting process, the liquid metal moving in the launders which are used during the transfer of the liquid metal to the casting machine, contains the mentioned particles. The T1B2 particles have a density of 4.52 g/cm3, which is higher than the density of liquid aluminum at 2.69 g/cm3.
For this reason, the particles settle down at the bottom of the launders and create agglomerations in time as they travel through the launder. When liquid metal samples taken from the lower and upper level of liquid metal moving in launders during casting of any aluminum alloy were chemically analysed, the Ti content of the sample from the lower level was measured as minimum of 300 ppm while this value was measured as less than 100 ppm for the sample taken from the upper level.
This observation confirms that T1B2 particles have settled down to the bottom of the launder. When the same samples were also examined metallographically, the agglomerated T1B2 particles and the accompanied oxide film and oxide particles were also clearly observed. As the amount of metal cast without any intermission increases over time, the amount of these formations also increases.
These agglomerations in the launders after a while are introduced to the flow of liquid metal then trapped inside the strip being solidified. If this strip will be processed into a thin gauge foil product, those will cause very important production defects and even will seriously impair the foil production process.
In the PCT document with publication number WO2010009326 aluminum or magnesium strip production by twin roll casting method has been mentioned. But in the mentioned invention, there is no mention to settlement or any mixing process to be applied in order to prevent the settlement. The United States Patent Office document with publication number US20100163204, mentions a kind of twin roll casting machine, the invention does not involve any mixing step before roll forming stage.
The Korean Patent Office document with publication number KR20150072752, mentions to the use of a twin roll casting method in strip production and mentioned invention does not involve any mixing method.
As a result, all above mentioned problems, made it necessary to make an innovation in the concerned field.
OBJECTIVE AND BRIEF DESCRIPTION OF THE INVENTION
The present invention makes it necessary to remove the above-mentioned problems and to make technical innovation in the relevant field.
The main objective of the invention is to prevent the settlement of T1 B2 particles at the bottom of the launder and to ensure their homogeneous distribution in the liquid metal which is moving towards the casting machine without causing agglomeration, and to prevent the occurrence of defects on the strip produced in the casting machine and to produce the desired product by rolling in ideal conditions.
Another objective of the invention is to remove the surface segregations that arise due to difference in grain size between the lower and upper surfaces of the strip.
Another objective of the invention is to prevent strip breaks during rolling of thin gauge foils due to the presence of T1B2 agglomerations and oxide particles that are trapped inside the material during solidification of the all kinds of foil products that are produced by rolling, obtained from the aluminum alloy and having thickness less than 15 micrometer.
Another objective of the invention is to minimize down time due to strip break, production losses and to maximize productivity. Another objective of the invention is to prevent use of excessive grain refining agent.
Another objective of the invention is to increase quality of the product by defects originating from the solidified metal itself.
Another objective of the invention is to extend the launder service life by preventing build-up of T1B2 and oxide deposits on the inner walls of the launders.
In order to accomplish all objectives mentioned above and will occur from the following detailed description, the present invention is the method that increases the product quality and productivity of the twin roll casting process used during foil and strip production with aluminum alloys, characterized in that at least one magnetic stirrer that enables homogeneous mixing inside the launder prior to solidification between caster rolls, of particularly a T1B2 particles and alloying elements used for initiation of solidification in aluminum alloy and grain refinement purpose, is positioned at lower or upper part of the said launder.
The present invention is a twin roll casting method characterized in that the method comprises a magnetic stirring unit which is externally mounted to the bottom of the launder system that allows homogeneous mixing of grain refiner particles in the melt during the production of an aluminum alloy. In a preferred embodiment of the invention, considering that the T1B2 particles build up agglomerates in the lower part of the launder, the method comprises a magnetic stirring unit operating at a frequency range of 100-140 Hz, with power of 80-100 kW, is positioned below the launder which is capable of agitating and making the liquid aluminum move from base of the launder base to the surface by evenly distributing the grain refiner particles in the melt.
In another preferred embodiment of the invention, magnetic stirrer with different power and frequency configurations are positioned at the lower region of the launder through the degassing unit between ladle and tundish and hot metal reservoir before the casting machine. DETAILED DESCRIPTION OF THE INVENTION
In this detailed explanation, twin roll casting method with magnetic stirrer unit subject to this invention is only explained with examples that will not have any limiting effect so that the subject can be understood better.
The magnetic stirrer application in twin roll casting method which is subject of the invention, is related to the innovation in aluminum alloy strip and foil production, that prevents the settlement of T1B2 grain refiner particles in the molten aluminum alloy at the bottom of the launder.
The present invention is related to the method that increases the product quality and productivity of the twin roll casting process used during foil and strip production with aluminum alloys, characterized in that at least one magnetic stirrer that enables homogeneous mixing inside the launder before solidification occurs between caster rolls, of particularly a T1B2 particles and alloying elements used for initiation of solidification in aluminum alloy and grain refinement purpose, is positioned on lower or upper part of the said launder.
The present invention is a twin roll casting method characterized in that the method comprises a magnetic stirring unit which is positioned at the bottom of the launder that allows homogeneous mixing of different elements contained inside liquid metal during the production of an aluminum alloy.
In strip production with aluminum alloy, in order to improve the microstructure and mechanical properties of the strip, those particles composed of Titanium and Boron elements are added by means of grain refining in aluminum.
In the production of aluminum strip/foil production by twin roll casting method (TRC), proper chemical composition of an alloy is prepared in the melting furnaces. Homogeneous distribution of elements which are added to liquid metal is realized by mechanical mixing in the melting furnaces and rotor in the degassing unit. T1B2 particles acting as nucleating agent in the course of solidification in between caster rolls is introduced to the liquid metal in the launders. Grain refiner rod, bearing T1B2 particles, is in the form of coil and mechanically fed into liquid metal flowing in the launder system. One of the essential instrument within the launder system is degassing unit. Since the position of adding grain refiner is before degassing unit, proper mixing of the T1B2 grain refiners particles is attained in the degasser, as well.
However, after leaving the degassing unit, the liquid metal again travels along the long launders. Due to the difference in specific density of T1B2 particles and liquid aluminum, T1B2 particles begin to settle down as they travel along the launder. Along with the contribution of oxide film and oxide particles, agglomeration of the T1B2 particles takes place and size of those formations increases with more liquid metal flows.
After degassing unit, aluminum in liquid state is then fed to the ceramic-based nozzle material. Design of ceramic nozzle regulates temperature and flow of liquid metal along its width of up to 2300 mm. The liquid metal is then delivered in between two water- cooled caster rolls.
Solidification of the liquid metal takes place on the surface of caster rolls. As the solidified metal moves in casting direction, it is slightly rolled to the intended thickness of as-cast strip. Chemical elements in the liquid metal and the amount and distribution of T1B2 particle determines the microstructural features of the as-cast sheet. The characteristics of the as-cast microstructure are very crucial for the performance of end product.
According to the results of the OES (Optical Emission Spectrometer) analysis of the samples taken from the base and the upper level of the launder that transfers the liquid metal, the Ti content of the samples taken from the base of the launder was found to be high. However, the other samples obtained from the upper level show low Ti content. T1B2 particles and extra Ti in the grain refiner rod are the only the only source of Ti. Since extra Ti is in solid and uniformly distributed in the OES samples, source of excessive Ti is T1 B2 particles.
The magnetic stirrer assembly which the invention comprises is placed underneath the launder system immediately before the liquid metal reservoir system, which is the region closest to the caster where the solidification takes place. The components of magnetic field created by the magnetic stirrer which is perpendicular to the launder base enable to re-introduce T1B2 particles to the main stream of the liquid metal preventing them to settle and keep them in suspension. Since there is no significant agglomeration of T1 B2 particles, coagulation of those particles with oxide film and particles are very unlikely.
Thus, the T1B2 particles, the oxide particles and films that may possibly exist and the alloying elements are homogeneously distributed in liquid aluminum by the help of magnetic stirring.
In the magnetic stirring system which is subject to the invention, a magnetic stirrer capable of working in the frequency range of 100-140 Hz and in the range of 80-100 kW, has been developed, to move liquid aluminum from the channel base to the surface, and has been placed below the channel considering that TiB2 particles settle to the base of the channel.
In other preferred embodiments of the invention, depending on the size of the launder used and varying density of the liquid metal due the amount of alloying element present, magnetic stirrers with different power and frequencies may be located at the lower and/or upper region of the channel which is in-between the degassing unit between holding furnace and tundish and hot metal reservoir before the caster.

Claims

1 . A method that increases the product quality and productivity of the twin roll casting process used during foil and strip production with aluminum alloys, the method comprising at least one magnetic stirrer that enables homogeneous mixing inside the launder before solidification takes place between caster rolls, of particularly a T1B2 particles and alloying elements used for initiation of solidification in aluminum alloy and grain refinement purpose, is located on lower or upper part of the said launder.
2. The method to improve the productivity and product quality of a twin roll casting process according to claim 1 , wherein at least one magnetic stirrer is located at the bottom of the launder between the degassing unit and the liquid metal reservoir before the casting machine.
3. A method of twin roll casting, the method comprising a magnetic stirrer unit positioned at the bottom of the twin roller channel, which allows homogenous mixing of the different metals in the liquid metal alloy during the production of the aluminum alloy.
4. Twin roll casting method according to claim 1 or claim 3, the method comprising a magnetic stirrer unit operable at a frequency range of 100-140 Hz.
5. Twin roll casting method according to claim 1 or claim 3, the method comprising a magnetic stirrer unit having a power of between 80-100 kW.
PCT/TR2017/050566 2017-01-11 2017-11-14 Twin roll casting method with magnetic stirrer WO2019017858A2 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
TR2017/00428 2017-01-11
TR201700428 2017-01-11

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP17918107.8A EP3565680A4 (en) 2017-01-11 2017-11-14 Twin roll casting method with magnetic stirrer

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WO2019017858A2 true WO2019017858A2 (en) 2019-01-24
WO2019017858A3 WO2019017858A3 (en) 2019-05-02

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Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2077145A1 (en) * 1991-08-29 1993-03-01 Julian Szekely Method and apparatus for the magnetic stirring of molten metal in a twin roll caster
US5518064A (en) * 1993-10-07 1996-05-21 Norandal, Usa Thin gauge roll casting method
KR100430065B1 (en) * 2000-11-22 2004-05-03 한국과학기술연구원 Strip Forming Device via Continuous Shear Deformation Combined with Strip Casting
US7048033B2 (en) * 2001-09-14 2006-05-23 Nucor Corporation Casting steel strip
JP2009208140A (en) * 2008-03-06 2009-09-17 Fujifilm Corp Manufacturing method of aluminum alloy sheet for planographic printing plate, aluminum alloy sheet for planographic printing plate and support for planographic printing plate manufactured by the method
KR20150072752A (en) * 2013-12-20 2015-06-30 주식회사 포스코 Methods of manufacturing metal strip using twin roll strip casting apparatus and looper shield therefor
CN103789599B (en) * 2014-01-28 2016-01-06 中广核工程有限公司 Continuous casting and rolling prepares B 4the method of C/Al neutron absorber material sheet material
CN105397045B (en) * 2015-12-21 2017-11-10 东北大学 The casting and rolling device and casting-rolling method of a kind of aluminum alloy slab

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WO2019017858A3 (en) 2019-05-02
EP3565680A2 (en) 2019-11-13
EP3565680A4 (en) 2020-05-27

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